1. Field of the Invention
This invention relates to a disc recording and/or reproducing apparatus for recording and/or reproducing information signals using a disc cartridge in which a disc is accommodated in a cartridge main body.
2. Description of the Related Art
There has hitherto been proposed a disc recording and/or reproducing apparatus for recording and/or reproducing information signals using a disc cartridge in which a disc, such as an optical disc or a magneto-optical disc, is accommodated in a cartridge main body.
The disc recording and/or reproducing apparatus includes a chassis on which there are mounted a loading unit for transporting the disc cartridge to a predetermined loading position, a rotating driving unit for holding and rotationally driving the disc in the disc cartridge at the loading position and an optical head unit for writing and/or reading information signals on or from the disc held by the rotating and driving unit.
The loading unit includes a cartridge holder for holding the disc cartridge introduced into the recording/reproducing apparatus. The cartridge holder, which may be moved vertically within the main body of the apparatus by means of a cam or the like, holds the disc cartridge in a parallel position with respect to the chassis. The loading unit first shifts the disc cartridge, held by the cartridge holder, in a direction parallel to the major surface of the disc, that is parallel to the chassis. When the disc is brought to a position directly above the rotating and driving unit, the loading unit shifts the disc cartridge vertically towards the chassis.
With the disc cartridge thus displaced towards the chassis, the disc housed in the disc cartridge is held by the rotating and driving unit provided on the chassis.
The optical head unit is mounted on the chassis for facing the major surface, the signal recording surface, of the disc which is rotationally driven by the rotating and driving unit. The optical head unit is supported for being moved radially and across the inner and outer peripheries of the disc. With the disc being rotated by the rotating and driving unit and with the optical head unit being moved radially of the disc, the light flux may be radiated by the optical head unit on substantially the entire signal recording surface of the disc, so that information signals may be recorded on or reproduced from substantially the entire signal recording surface of the disc.
The optical head unit is also provided with an object lens driving device for performing focusing and tracking servo operations for causing the light flux radiated on the disc to follow deviations from a horizontal plane or concentric positions caused by disc rotation. The object lens driving device supports an object lens converging and radiating the light flux by a supporting member formed of a flexible material so that the object lens may be moved in two directions, that is in a direction along the optical axis and a direction perpendicular thereto. The object lens driving device also includes an electro-magnetic driving device for moving the object lens in these two directions. This electro-magnetic driving device includes a coil which is mounted on a lens bobbin supporting the object lens and which is supplied with a driving current based on focusing and tracking error signals employed in the focusing servo and tracking servo operations, and a magnetic circuit for passing the magnetic flux through the coil.
In the above-described disc recording/reproducing apparatus, it is difficult to simplify the construction and manufacture and to reduce the size of the apparatus because of the complex structure of the loading unit adapted for moving the disc cartridge in the horizontal and perpendicular directions.
Besides, it is also difficult with the above-mentioned disc recording and/or reproducing apparatus to simplify the construction and reduce the size of the optical head unit because the optical head unit needs to be provided with the above-described object lens driving device.
It may be contemplated to use a small-sized disc to reduce the size of the disc recording and/or reproducing apparatus. However, if the disc of the smaller size be used for reducing the size of the disc recording and/or reproducing apparatus, the recording capacity for the information signals is diminished, so that the advantages of a large capacity information storage device may be lost.